1. Technical Field
The present invention relates to control of humidity lined or unlined bulk cargo containers. In particular, it relates to suspendable moisture absorbant such as desiccant panels which reduce or increase humidity depending on the nature of the cargo.
2. Background Art
Transportation of containers for bulk commodity products (grains, etc.) have been implemented using a variety transport vehicles, such as trucks, railroads, and ships. Initially, containers developed to haul cargo were simple storage devices which did not address environmental concerns. However, due to the long time delays in shipping commodities in large markets, and the nature of many commodity goods, the value of commodities can be significantly reduced. This is true not only for perishable goods such as foods, but also for other goods such as automobiles, electronics, computers, or military equipment which can be subject to damage from rust during shipment from factories or to remote areas with harsh climates. Therefore, an important economic factor in the transportation of commodities is the deterioration of the commodities due to adverse environmental factors, such as humidity.
The prior art has addressed environmental factors in several ways. For example, insulated containers such as those having on-board refrigeration can preserve commodities for longer periods. However, not all commodities are suitable for shipping under refrigeration. In addition, refrigeration containers are expensive manufacture and expensive to operate due to fuel consumption.
Another method of protecting commodities from environmental factors has been the development of liners. While improving on the level of humidity control, liners are limited by their passive nature. Due to the passive nature of liners, and to the substantial changes in humidity that occur as a container is transported through various weather systems, cargo damage due to humidity remains a concern for numerous perishable commodities.
The use of desiccant bags to reduce humidity can be implemented, but desiccant bags create additional problems in that it is undesirable to loosely place these bags in a liner or a container without a liner because they can interfere with the loading and unloading process. The use of many small desiccant bags may also cause the dehumidification process to be localized in certain areas of the cargo, resulting in uneven benefit and reduced usefulness. In addition, the use of loose desiccant bags is undesirable since a leak in one of the loose bags, caused by defect, mishandling, or damage done during shipment, may contaminate certain cargo such as foodstuffs.
It is known that liners can be evacuated after loading by withdrawing air via a pump. In this manner, the liner is compressed around the cargo, much like consumer products are shrink wrapped. A drawback associated with this approach is the expense involved with the evacuation equipment, as well as the extra labor involved to ensure that the liner is properly sealed. Further, since container sized liners are apt to have some small leaks, the pump may have to be transported on the container to periodically restore the vacuum. Of course, since evacuation can only serve to reduce humidity, it is of no use in situations were a higher humidity is desirable.
While addressing the various environmental aspects of transporting bulk commodities in container systems, the prior art has produced various methods such as refrigeration systems which are useful for a subset of the products shipped by container, liners used alone or with loose desiccant bags, or liner evacuation systems. While the prior art approaches solve various problems associated with transportation of bulk cargo, they have not provided an active humidity control system which is easily installed, is inexpensive to use, avoids contamination of cargo, does not interfere with loading or unloading, and can be used to either increase or decrease humidity depending on the nature of the cargo.